Add basic meta info file parsing

1 files changed, 47 insertions, 0 deletions

diff --git a/src/metainfo.zig b/src/metainfo.zig
new file mode 100644
index 0000000..9fa4788
--- /dev/null
+++ b/src/metainfo.zig
@@ -0,0 +1,47 @@
+//! https://wiki.theory.org/BitTorrentSpecification#Metainfo_File_Structure
+const std = @import("std");
+const bencode = @import("bencode.zig");
+const MetaInfo = @This();
+
+pub const Info = struct {
+    pub const File = struct {
+        name: []const u8,
+        length: u64,
+        path: []const u8,
+    };
+    piece_length: u64,
+    pieces: []const u8,
+    files: []File,
+    pub fn parse(b: bencode.BValue) !Info {
+        var d = b.asDict() catch return error.Malformatted;
+        const pl = d.get("piece length") orelse return error.Malformatted;
+        const pp = d.get("pieces") orelse return error.Malformatted;
+        return .{
+            .piece_length = pl.asInt(u64) catch return error.Malformatted,
+            .pieces = pp.asString() catch return error.Malformatted,
+            .files = &[_]File{},
+        };
+    }
+};
+
+info: Info,
+announce: []const u8,
+
+pub fn parse(b: bencode.BValue) !MetaInfo {
+    var d = b.asDict() catch return error.Malformatted;
+    const i = d.get("info") orelse return error.Malformatted;
+    const a = d.get("announce") orelse return error.Malformatted;
+    return .{
+        .info = try Info.parse(i),
+        .announce = a.asString() catch return error.Malformatted,
+    };
+}
+
+test "sample" {
+    const a = std.testing.allocator;
+    const sample_str = @embedFile("sample.torrent");
+    var b = try bencode.bdecodeBuf(a, sample_str);
+    defer b.deinit(a);
+    const mi = try MetaInfo.parse(b);
+    try std.testing.expectEqualStrings("http://bittorrent-test-tracker.codecrafters.io/announce", mi.announce);
+}